Ultrasonic transit time measurements are being used to continuously record fetal head descent and cervical dilatation during labor. Assuming a constant velocity for ultrasound in the maternal pelvis, one is able to measure the transit time between ultrasonic transducers located over the right and left iliac crests and symphysis pubis on the maternal abdomen and located on the fetal presenting part. In addition, the transit time is measured between two transducers on opposite sides of the rim of the external os of the cervix. These transit time measurements then give displacement after appropriate calculations have been made, by passing the data through a digital computer. The results can be plotted on axes referred to the maternal pelvis, to assess the progress of labor. Recordings give curves similar to digitally determined progress of labor curves, but in addition they show changes in descent and dilatation with each uterine contraction with a return to near baseline conditions following the contraction.